x1,y1,x2,y2 = map(float,input().split())
an = (x1 - x2)**2 + (y1 - y2)**2
dis = an/2
v = an/4
while abs(dis**2 - an) > 0.0001:
	if dis**2 > an:
		dis -= v
	else:
		dis += v
	v = v/2
print(dis) x1,y1,x2,y2 = map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 an = (x1 - x2)**2 + (y1 - y2)**2 an (x1 - x2)**2 + (y1 - y2)**2 (x1 - x2)**2 x1 - x2 x1 x2 2 (y1 - y2)**2 y1 - y2 y1 y2 2 dis = an/2 dis an/2 an 2 v = an/4 v an/4 an 4 while abs(dis**2 - an) > 0.0001:
	if dis**2 > an:
		dis -= v
	else:
		dis += v
	v = v/2 abs(dis**2 - an) > 0.0001 abs(dis**2 - an) abs dis**2 - an dis**2 dis 2 an 0.0001 if dis**2 > an:
		dis -= v
	else:
		dis += v
	 dis**2 > an dis**2 dis 2 an dis -= v dis v dis += v dis v v = v/2 v v/2 v 2 print(dis) print dis x2,y2 = map(float,input().split()) map(float,input().split()) x2 an = (x1 - x2)**2 + (y1 - y2)**2 (x1 - x2)**2 + (y1 - y2)**2 an x1,y1,x2,y2 = map(float,input().split()) map(float,input().split()) x1 v = an/4 an/4 v dis += v v dis y2 = map(float,input().split()) map(float,input().split()) y2 dis -= v v dis dis = an/2 an/2 dis y1,x2,y2 = map(float,input().split()) map(float,input().split()) y1 v = v/2 v/2 v
x1,y1,x2,y2 = map(float,input().split())
an = (x1 - x2)**2 + (y1 - y2)**2
dis = an/2
v = an/4
while abs(dis**2 - an) > 0.0001:
	if dis**2 > an:
		dis -= v
	else:
		dis += v
	v = v/2
print(dis)
